Alpha problem in houdini review publish


We are having a weird problem (Please find attatched image). It seems like alpha is not premulitiplied before burning to .mp4

Things to recreate:
create a basic smoke simulation in houdini
publish using review option

Could you manually render the openGL rop node in /out and share one of the PNG output files? I suspect that what you’re experiencing might actually already be present in the OpenGL rop node’s output which is a Houdini native node which renders out the view.

Could you also screenshot maybe what you expected as an output instead (if you have it)

Sure, here is the snapshot with the native OpenGL node inside Houdini.

Also attaching the image with premulitplied correct preview

This is happening only in DJV, It was fine when opened with Mr.viewer.
Seems like when burning .mp4 its rendering without premulitplying

This is great - do you have a sample PNG sequence from your particular output, something we could e.g. try the transcoding on to see if we can get the right output from the transcoding process itself?

@antirotor @iLLiCiT any idea how we could influence the transcoding process for Houdini reviews to perform this correctly?

Sure, here is the sequence.

I’ve just tested direct output from OpenGL node in png format and it has straight (not premultiplied) alpha. I couldn’t find any option to change this behaviour. OpenImageIO can premultiply so maybe we can add extractor for Houdini that will do that? Not sure how it behaves with other output formats like exrs, if it stores alpha as straight - but since it is coming from OpenGL I guess so.